A former bishop has ended Paraguay's 61 years of one-party rule, beating the reigning party's candidate to win the country's presidential election.

Late last night, Fernando Lugo, a mild-mannered leftist who quit the clergy three years ago, saying he felt powerless to help Paraguay's poor, was announced as the winner of the elections after some uncertainty.

Lugo had been given 40 to 43% of the vote in four separate exit polls earlier in the evening. The ruling Colorado party's candidate, Blanca Ovelar, the first woman to run for president in Paraguay, was on 36 to 38%.

Ovelar, 50, a former education minister and protege of the outgoing president, Nicanor Duarte, at first refused to concede, predicting she would score heavily in rural areas beyond the reach of the exit pollsters. But with Lugo nine points up after partial counting of votes, she gave way.

Another candidate, retired army general Lino Oviedo, freed last year after the supreme court overturned a sentence for plotting a coup, was in third place.

"We ask you never to abandon us. We'll make democracy together!" Lugo, 56, told cheering supporters as firecrackers resounded around Asuncion last night.

Lugo, nicknamed the "bishop of the poor", was confident Paraguayans would elect him in the hope of seeing "a different country", likening himself to a David fighting a "monstrous Goliath". The Colorado party has stayed in power by means of democracy and dictatorship, ruling even longer than Cuba's Communist party.

Eight months ago, Lugo welded unions, Indians and poor farmers into a coalition with the main opposition party to form the Patriotic Alliance for Change.

Many ordinary Paraguayans had become fed up of what they saw as a corrupt establishment, that failed to safeguard the poorest in a country landlocked by wealthier neighbours Argentina and Brazil, and economically dependent on its agricultural and hydroelectric power exports.

Lugo campaigned heavily on trying to charge Brazil more money for the power it imports from the jointly owned Itaipu hydroelectric plant - following in the footsteps of Bolivia, which negotiated to charge its neighbours more for natural gas.

Lugo calls himself an independent and has steered clear of Latin America's more radical leftwing leaders, such as Venezuela's Hugo Chávez and Evo Morales in Bolivia. But he is seen as a likely ally of moderate leftist presidents in the region.

Lugo will take office on 15 August, and has vowed to carry out agrarian reform to ensure poor peasant farmers can till their own land in a country where a small, wealthy elite owns the vast majority of farmland and cattle ranches.